1. Field of the Invention
The present invention relates to a connecting structure of a liquid sending apparatus having an electroosmotic flow pump using an electroosmosis phenomenon, a fuel-cell type electricity generating apparatus having the connecting structure of the liquid sending apparatus, and an electronic device having the fuel-cell type electricity generating apparatus.
2. Description of Related Art
In recent years, fuel-cells receive attention as clean power supplies having high energy conversion efficiency, and the fuel-cells become commercially practical for fuel-cell automobiles, portable devices, electrical houses.
In the fuel-cell, a pump is used as a power source for sending fuel or water. There are centrifugal type pumps, volume rotary type pumps, volume reciprocating type pumps which are mechanically operated. For example, Japanese Patent Application Laid-open No. 2006-22807 discloses an electroosmotic flow pump which sends liquid without having a mechanically movable portion.
The electroosmotic flow pump uses an electroosmosis phenomenon, and has a structure as shown in FIG. 18. As shown in FIG. 18, the electroosmotic flow pump includes an electroosmosis material 502 charged into a tube member 504, an electrode 501 disposed upstream from the electroosmosis material 502, and an 503 disposed downstream from the electroosmosis material 502. The electroosmosis material 502 comprises a dielectric such as a silica fiber disposed along a flowing direction of the tube member 504.
The electroosmotic flow pump is operated in accordance with the following principle. That is, if liquid comes into contact with the dielectric of the electroosmosis material 502, a surface of the dielectric is electrically charged, counter ions in the liquid gather around the contact interface, and the number of electric charges becomes excessively large. Hence, if voltage is applied between the electrode 501 and the electrode 503 and an electric field is generated in the electroosmosis material 502, counter ions in the liquid move, and the entire liquid flows due to the viscosity of the liquid. When the electroosmosis material 502 is silica, a surface of silica becomes Si—O—, the silica surface is negatively charged, plus ions (counter ions) gather in the liquid, and the number of plus electric charges becomes excessively large in the liquid. Thus, if voltage is applied such that the potential of the electrode 501 becomes higher than that of the electrode 503, the fluid flows in the direction as shown in FIG. 18.
The electroosmotic flow pump is operated in accordance with such a principle, and has a merit that there is no movable portion, the pump can be made compact, and the pump does not create pulsation and noise.
Japanese Patent Application Laid-open No. 2006-95958 proposes an electroosmotic flow pump having a self-filling mechanism and a gas-draining mechanism for driving liquid.
However, if a liquid-sending operation is continued by the electroosmotic flow pump, bubbles are generated due to electrolysis of liquid in the vicinity of both the electrodes. Thus, bubbles generated around the upstream electrode are accumulated on the upstream side, an effective flow-path area of the electroosmosis material is reduced and there is a fear that the liquid sending efficiency is deteriorated. Bubbles generated around the downstream electrode flows downstream together with liquid, there is a fear that a flow rate sensor provided downstream can not detect a precise flow rate of liquid due because bubbles pass.